The present invention relates to an improved activated alumina catalyst having high activity and selectivity for prolonged periods of time when employed in a process for the production of ethylene from ethanol through a dehydration reaction.
For effecting the catalytic dehydration of ethanol in the vapor phase there have hitherto been utilized, as catalyst, silica-alumina, activated alumina, solid phoshoric acid, metal sulfate, etc. These catalysts, however, are observed to be defective in that the activity thereof is significantly decreased by the deposition of carbonaceous material on the surface of the catalyst during the course of the reaction, a satisfactorily high ethylene yield can not be obtained because ether, aldehyde, C.sub.4 -olefins, etc. are easily by-produced and so forth. In order to eliminate these defects there have been considered such counterplans that the reaction is operated at a high space velocity thereby suppressing the conversion rate of ethanol to a low degree, and the partial pressure of ethanol is decreased by the use of diluent gas.
We have devoted ourselves to investigations to develop a catalyst capable of eliminating the above mentioned defects inherent in conventional catalysts and exhibiting high efficiency as well as stability in the formation of the final product ethylene. Consequently, we have discovered the facts that a high purity alumina catalyst containing extremely reduced amounts of the remaining alkali metal, sulfur, iron and silicon components can exhibit high activity and high selectivity in the formation of ethylene and that the addition of a small amount of a certain kind of metal phosphate to said alumina can impart a high stability in addition to the aforesaid high activity and high selectivity. Through these processes of investigations, we have succeeded in developing an activated alumina catalyst capable of totally removing the defects inherent in conventional catalysts and thus completed the present invention.